In general, a combustor of a gas-turbine is placed in the vicinity of an outer periphery of a backside of a compressor. The role of the combustor includes, spraying fuel to the air discharged from the compressor, combusting the fuel to produce high-temperature and high-pressure gas for driving the turbine, and introducing the combustion gas to a nozzle (stationary blade) of a gate of the turbine. Since a liner (inner cylinder) and a transition piece (tail cylinder) in a combustion engine are exposed to the combustion gas at 1500 to 2000° C. and heated to 700 to 900° C. by the exposure, the liner and transition piece are required to maintain their shapes at that temperature. In addition, the liner and the transition piece suffer severe heat cycle of heating and cooling that accompany frequent starting, stopping, and power controlling.
Therefore, a material used in the production of liners and transition pieces of gas-turbine combustors is required to have excellent high-temperature strength such as high-temperature tensile strength, creep-rupture strength, low-cycle fatigue strength, and thermal fatigue strength, and is further required to have high-temperature corrosion resistance such as high-temperature oxidation resistance, and high-temperature sulfidization resistance. In addition, the liners and transition pieces of combustors are produced by hot-working and cold working of various Ni-based heat resistant alloy plates, brazing the plates, and welding the plates. Therefore, the material is also required to have cold-workability, hot-workability, and brazability.
Conventionally, Ni-based heat-resistant alloy has been used as a material for liners and transition pieces of the combustors. Specific examples of the Ni-base heat-resistant alloy which have been used in the prior art include: a solid-solution strengthened type alloy or a slight precipitation-strengthened type alloy represented by Ni-base heat resistant alloy composed of, in mass % (hereafter, % denotes mass %), 22% of Cr, 1.5% of Co, 18.5% of Fe, 9% of Mo, 0.6% of W, 0.1% of C, and a balance of Ni, and Ni-based heat resistant alloy composed of 22% of Cr, 8% of Co, 9% of Mo, 3% of W, 1% of Al, 0.3% of Ti, 0.07% of C, and a balance of Ni; or precipitation strengthened type alloy such as Ni-based heat resistant alloy composed of 20% of Cr, 20% of Co, 5.9% of Mo, 0.5% of Al, 2.1% of Ti, 0.06% of C, and a balance of Ni.
Further, a Ni-based heat resistant alloy of the following constitution has been proposed as a material for a gas turbine engine. The alloy has a composition containing Cr: 15.0 to 30%, Co: 5 to 20%, Mo: 6 to 12.0%, W: up to 5%, Zr: up to 0.5%, Al: 0.5 to 1.5%, Ti: up to 0.75%, C: 0.04 to 0.15%, B: up to 0.02%, Fe: up to 5%, rare earth element: up to 0.2%, and a balance consisting of Ni and unavoidable impurities. The alloy is further characterized by substantially recrystallized fine structure, wherein at least 1 to 2 weight % of the alloy is constituted of M6C carbide, and lesser % of the alloy is constituted of M23C6 carbide, where the M6C carbide constitutes at least 50% of existent carbide in the alloy, and crystal grains have an average size of about 3 to about 5 in ASTM#. The M6C carbide dispersed in the matrix of the Ni-based heat resistant alloy has a diameter of 3 μm or less, TiN phase in an amount of 0.05% or less is included in the matrix of the Ni-based heat resistant alloy, and inter-metallic compound represented by Ni3(Al,Ti), that is γ′ phase, exist in an amount up to 5% (Japanese Unexamined Patent Application, First Publication No. H2-107736).